Unfortunately, in the real world, family does often do counterproductive things, especially when serious religious beliefs are involved.

I suspect that one of us, probably both, are falling prey to the Typical Family Fallacy. It's similar to the Typical Mind Fallacy, only it applies to families instead.

By the way, what would you suggest to a gay teenager who is afraid that telling the truth would lead to getting thrown out of the house?

I'd recommend making sure to have someplace to move to prepared, in advance, before telling his parents. (This might take a few years to set up). The negative consequences, in such a case, appear sufficiently bad to justify caution, even temporary concealment of the truth.

I'd also recommend finding some other mentor, or authority figure, that he can trust to talk about the situation with. This other mentor might be a school counsellor, a priest, an aunt or uncle, a teacher, or a school janitor; anyone reasonably sensible who would be willing to not inform his parents would do.

It's not right to describe that as "to grab the tempting benefits" when the "benefit" consists of not being harassed.

That seems like a pretty tempting benefit to me.

"Lie, because someone else might lie" certainly isn't a good description of lying to conceal your beliefs.

That is true. It does apply to some other forms of "lie to grab the tempting benefits", though.